Refactor: CTS: Update add_cmd calls in cts-exec.

These need to be updated for the changes to the Test class.

• Change function headers to match the superclass versions.

• Because none of the callers pass cmd=, default it to be self._test_tool_location. This means we don't have to further modify all the callers to additionally pass the command name as well.

• Clean up some of the quoting used when calling these functions. Basically, change double quotes to single quotes so we can reduce some of the unnecessary escaping.

• Remove unnecessary quotes around arguments that don't contains spaces or other characters that need to be escaped.

• Remove unnecessary parens around single element tuples in string substutitions.

I only did these quoting and paren cleanups to callers that I was
already modifying. There's plenty more that needs to be done in this
file before the python checkers are happy.